1. Field of the Invention
The invention relates to an improved bubble cap assembly in an ebullated bed process. Specifically, the invention is the combination of a bubble cap assembly with an improved fluid outlet port position to prevent check ball on cap wear. The invention is also a combination of the bubble cap assembly with an orifice mixer to homogenize the gas and liquid phases flowing through the bubble cap assembly. The combination promotes steady flow of fluid causing reduced wear of bubble caps such as those described in U.S. Pat. No. 3,475,134.
2. Description of Relevant Methods in the Field
The ebullated bed process comprises the passing of concurrently flowing streams of liquids or slurries of liquids and solids and gas through a vertically cylindrical vessel containing catalyst. The catalyst is placed in random motion in the liquid and has a gross volume dispersed through the liquid medium greater than the volumne of the mass when stationary. This technology has found commercial application in the upgrading of heavy liquid hydrocarbons or converting coal to synthetic oils.
The process is generally described in U.S. Pat. No. Re. 25,770 to Johanson incorporated herein by reference. A mixture of hydrocarbon liquid and hydrogen is passed upwardly through a bed of catalyst particles at a rate such that the particles are forced into random motion as the liquid and gas pass upwardly through the bed. The catalyst bed motion is controlled by a recycle liquid flow so that at steady state, the bulk of the catalyst does not rise above a definable level in the reactor. Vapors along with the liquid which is being hydrogenated pass through that upper level of catalyst particles into a substantially catalyst free zone and are removed at the upper portion of the reactor.
In an ebullated bed process the substantial amounts of hydrogen gas and light hydrocarbon vapors present rise through the reaction zone into the catalyst free zone. Liquid is both recycled to the bottom of the reactor below a distributor plate and removed from the reactor as product from this catalyst free zone. Vapor is separated from the liquid recycle stream before being passed through the recycle conduit to the recycle pump suction. The recycle pump (ebullating pump) maintains the expansion (ebullation) and random motion of catalyst particles at a constant and stable level.
Reactors employed in a catalytic hydrogenation process with an ebullated bed of catalyst particles are designed with a transverse distributor plate which distributes the feed hydrocarbon liquid and hydrogen uniformly to three phase expanded bed of catalyst in order to maintain a stable, random motion within the bed. The transverse distributor plate also serves as a partition to separate hydrocarbon liquid and hydrogen feed streams from the expanded catalyst bed and provides physical support for the elevated catalyst bed within the reactor.
U.S. Pat. No. 3,475,134 issued Oct. 28, 1969, to C. L. Weber and R. H. Wolk incorporated herein by reference describes a transverse distributor plate comprising a bubble cap and plate assembly. The bubble cap comprises a ball check valve mounted on a valve seat, the valve seat comprising an orifice. The ball seals the orifice to back flow of solid catalyst while permitting drainage of liquid off the distributor plate during shut down. At flow conditions, the ball is lifted off the seat. The valve seat orifice is sized to accelerate the up flowing fluids through the valve to assure up flow of solids and to prevent down flow through the valve during transient or disrupted flow.